DOSCab will have two options for radio mode:
1) Random song: Pick a song at random
2) Popular songs: Pick a song at random from the top 100 songs, weighted more toward the top of the list.
Either way, you can set the number of songs to play before repeats are allowed, i.e. if the repeat value is 10, none of the last 10 random songs will be played.
This is, of course, presuming I ever have time to work on the darn thing...